1. Technical Field
The present invention relates to an organic light-emitting diode (OLED) display and, more particularly, to an OLED display which can improve the problem of non-uniform luminance of pixels caused by IR-drop.
2. Description of the Related Art
OLED (Organic Light-Emitting Diode) panel employs OLED as light-emitting element. The OLED is driven by current, and the luminance thereof changes with the current passing through the OLED. Therefore, how to accurately control the value of the current passing through the OLED is an important problem of developing the OLED panel.
Referring to FIG. 1, a schematic view of a conventional OLED display is shown. The OLED display 100 comprises a scan driving circuit 110, a data driving circuit 120, a power supply 130 and an OLED panel 140. The OLED panel 140 comprises a plurality of scan lines (as shown by mark 142), a plurality of data lines (as shown by mark 144), a conducting wire 146 and a plurality of pixels (as shown by mark 148). Each of the pixels 148 is composed of a transistor 148-1, a transistor 148-2, a capacitor 148-3 and an OLED 148-4, and OVSS as shown in FIG. 1 is a reference voltage. The coupling relation of the above elements is shown in FIG. 1 and is not described herein. In addition, the pixels 148 are arranged in an array to form a display region of the OLED panel 140 for displaying images or words.
In the structure as shown in FIG. 1, the transistor 148-2 of each of the pixels 148 is electrically coupled to a voltage OVDD supplied by the power supply 130 through the conducting wire 146, so as to obtain a display potential (as shown by mark OVDD′). The cathode of the OLED 148-4 of each of the pixels 148 is electrically coupled to the reference voltage OVSS to obtain a reference potential. The data voltage transmitted by a corresponding data line 144 and the potential difference between the display potential OVDD′ and the reference potential will jointly influence the value of the current passing through the OLED 148-4 and thereby control the luminance of the OLED 148-4.
Generally, the value of the reference potential is constant. However, the values of the display potentials OVDD′ of the pixels 148 are different from each other because the locations of the pixels are different. That is, the current supplied by the power supply 130 is transmitted to different pixels 148 through different current-transmitting paths, and the different current-transmitting paths cause different voltage drops (that is the IR-drop). Thus, the display potentials OVDD′ received by the pixels 148 are different from each other.
In summary, since the display potentials OVDD′ received by the pixels 148 are different from each other, the currents of the OLEDs 148-4 are different from each other. Thus, the luminance of the OLEDs 148-4 is non-uniform. In other words, the IR-drop will cause the non-uniform luminance of the pixels 148.